This invention relates to a bearing assembly carrying a rotational speed sensor unit for sensing the rotational speed of e.g. a wheel of a vehicle.
Today's vehicles are equipped with a variety of increasingly sophisticated control systems, including anti-lock brake systems (ABS), which control the braking forces to individual wheels during hard braking to prevent lock-up of any wheel or wheels, traction control systems, which control the drive wheels to prevent either of them from slipping while the vehicle is accelerating, and car navigation systems. All of these systems require rotational speed sensor units for accurately measuring the rotational speeds of the wheels. Today, bearing assemblies including such rotational speed sensor units are becoming increasingly popular.
Unexamined JP patent publication 6-308145 discloses such a bearing assembly.
This bearing assembly is shown in FIG. 6. It comprises an outer member 2 having two raceways on the radially inner surface thereof, an inner member 3 having two raceways each radially opposing one of the raceways of the outer member, two rows of rolling elements, each row being disposed between one of the two pairs of radially opposed raceways, and a sensor unit. The sensor unit comprises a pulse generator 8 mounted on the inner member 3, which is rotational, and a sensor 12 mounted on the stationary outer member 2 so as to oppose the pulse generator 8.
The sensor 12 is inserted into and clipped on an annular sensor holder 6 fitted on the outer periphery of the outer member 2 near its inboard end.
The sensor holder 6 comprises a ring portion 7 fitted on the outer periphery of the outer member 2 near its inboard end, and a frame-shaped pocket 9 into which the head of the sensor 12 is inserted.
The pocket 9 includes guide portions 9a adapted to engage in guide grooves 12a formed in the side walls of the head of the sensor 12, and an elastic clip portion 9b adapted to engage in an engaging groove 12b formed in the front side of the sensor head. The head of the sensor 12 can thus be clipped on the sensor holder 6 utilizing the elasticity of the clip portion 9b. With the sensor head clipped on the sensor holder 6, the elastic clip portion 9b keeps the sensor 12 from disengaging from the pocket 9 in a radial direction of the inner and outer members, as long as the clip portion 9b is engaged in the engaging groove 12b, which extends across the center of the front side of the sensor 12.
But if a force indicated by the letter F in FIG. 7 is applied to the upper portion of the sensor 12, the sensor 12 will pivot counterclockwise (in FIGS. 6 and 7) from its upright position (FIG. 6) to the position shown in FIG. 7, thereby pushing the clip portion 9b out of the groove 12b. In this state, the clip portion 9b cannot rigidly hold the sensor 12 any more, so that the sensor 12 tends to disengage from the pocket 9 in a radial direction of the bearing inner and outer members.
An object of the invention is to provide such a sensor unit with means for keeping the sensor rigidly and stably held in the sensor holder by positively preventing the sensor from disengaging from the sensor holder in a radial direction of the bearing inner and outer members.